WEDNESDAY, Dec. 18, 2013 (HealthDay News) -- Older women with heart disease might be at increased risk for dementia, according to a new study.

Researchers followed nearly 6,500 U.S. women, aged 65 to 79, who had healthy brain function when the study started. Those with heart disease were 29 percent more likely to experience mental decline over time than those without heart disease.

The risk of mental decline was about twice as high among women who'd had a heart attack as it was among those who had not. Women who had a heart bypass operation, surgery to remove a blockage in a neck artery or peripheral artery disease also were at increased risk for mental decline.

Heart disease risk factors such as high blood pressure and diabetes also increased the risk for mental decline, but obesity did not significantly boost the risk, according to the study, which was published in the Dec. 18 issue of the Journal of the American Heart Association.

"Our study provides further new evidence that this relationship [between heart disease and dementia] does exist, especially among postmenopausal women," study author Dr. Bernhard Haring said in a journal news release.

"Many different types of heart disease or vascular disease are associated with declining brain function," said Haring, a clinical fellow in the Comprehensive Heart Failure Center and the department of internal medicine at the University of Wurzburg, in Germany.

Although the study found an association between heart disease and an increased risk of dementia in older women, it did not establish a cause-and-effect relationship.

"Women with heart disease -- in particular women who have had a heart attack, bypass surgery, heart failure, atrial fibrillation, peripheral vascular disease or carotid endarterectomy -- should be monitored by their doctors for potential [mental] decline," Haring said. "It is also very important to adequately manage heart disease risk factors such as high blood pressure and diabetes."

Further research is needed to examine how preventing heart disease might reduce the risk of dementia, the researchers said.